The Corps of Discovery did little to alter the land they passed through, but change would come soon enough. The historian Henry Adams pointed out that even as Lewis and Clark were laboring upstream on the Missouri with oar and simple sail, Robert Fulton was working on his first successful steamboat. The steamboat would come riding on the flow of the inevitabl--technological progress and emigration.

Clark would live to see some of the changes; Lewis would not. After serving as superintendent of Indian affairs and governor of the Missouri Territory, Clark died in 1838, at the age of sixty-nine. Lewis committed suicide in 1809, at the age of thirty-five. Jefferson lost a friend, but also felt that the world had lost an important body of scientific knowledge, for Lewis failed to publish his own edition of the journals.

We now know far more about the expedition than most nineteenth-century Americans did. The first full edition of the journals—a million or so words—appeared in the centennial year of 1904.

And, of course, we know far more about the land they described. For the reader who comes to Lewis and Clark for the first time, the undiscovered country is not the West but the past; their words connect us to their time and, more interestingly, to themselves.

In the end, the journals are highly personal documents, full of "first impressions of the mind." Lewis and Clark blazed a trail, but their words did not use up the subject. As long as there are new eyes to see it, new voices to tell about it, every land waits to be discovered.